This invention relates to the conducting of separation tests on coal by the submersion of coal in various organic liquids of different specific gravity, and more particularly, to an improved coal washability table with means for effective control of toxic vapors both during the running of the tests, and when the table is not in use.
Conventionally, coal separation testing is achieved by the immersion of a basket of coal, sequentially within a series of organic liquids carried respectively by multiple tanks normally located side-by-side. Depending upon the specific gravity of the coal (determined principally by its ash content) and that of the organic liquid within which the coal is immersed, the percentage of coal having a particular ash content may be readily determined as a result of the amount of floatation of the coal within a given tank. Typically, such tanks have been formed of stainless steel and the tank borne organic liquid tends to create toxic and/or noxious vapors which may be hazardous to the person conducting the tests.
Efforts have been made within recent years in conformance with governmental requirements, to eliminate such hazardous exposure of the test personnel of toxic vapors resulting from the coal washability tests.
In the chemical testing field, attempts have been made to provide sink constructions or multiple tank arrays which are open at the top to permit the placement and removal of objects within the sump area or tank and wherein ventilation is provided to the sump area itself or to portions of the apparatus immediately surrounding the sump to reduce the hazardous exposure of the operator or test personnel to toxic vapors resulting from such tests.
One type of sink construction employing a built-in ventilation feature appears in U.S. Pat. No. 3,376,583 issued to L. O. Frey, Apr. 9, 1968.
The sink construction of that patent takes the form of a rectangular sink bearing a recessed basin mounted within the center of a counter or table top and centered with respect to the longitudinal ends of the table. The basin is surrounded by a shell of larger size to form a narrow air space therebetween. The shell terminates at its top in a laterally extending flange forming a horizontal frame, the flange being provided with a right angle lip projecting into the interior of the basin; whereby, a vapor removal passage is formed between the basin and the shell. This passage is connected to a vacuum fan by way of a pipe to remove the vapor from the immediate area of the basin, which vapor is generated within the basin proper.
While the air ventilation means is quite effective in removing vapor generated within the basin itself, it has little effect on vapors existing or generated exterior of the basin and to the lateral sides or to the rear of the sink.
Where a plurality of tanks bear hot solutions of chemical substances within which metal parts may be dipped for cleaning purposes, attempts have been made to provide air ventilation to the surface area of the liquids carried by the tanks so as to exhaust noxious fumes eminating therefrom, commonly through a duct system coupled to ventilation means cooperating with one or more of the tanks. U.S. Pat. No. 2,110,991 to Carl S. Gabelson, issued Mar. 15, 1938, is representative of such tank constructions. In that apparatus, a plurality of open top rectangular tanks are mounted side-by-side, and being spaced slightly from each other in some cases, to define vertical ventilation paths between laterally oppposed sidewalls of respective adjacent tanks. Further, the bottoms of the tanks are supported at some height relative to a common casing surrounding all of the tanks to therefore define a common longitudinal flow path leading to a common collector duct subject to a slight vacuum pressure and acting to remove vapor generated within the interior of the tanks and moving into the common duct by way of the vertical passages formed by the sidewalls of adjacent tanks. Again, this type of air ventilation for ventilating the interior of the tanks acts to remove vapors generated within the tanks themselves, but has little effect on vapors emanating from the outside or created in the vicinity of the sump tanks bearing the liquid chemicals.
Within the more recent times, noxious or toxic vapors have been removed from an immediate work area by utilization of expensive and complicated clean room work stations involving hoods overlying the work area. Blowers and the like provide positive air pressure zones or the creation of vacuum pressure air flow through a frontal access opening and into the work station area to prevent the toxic or noxious vapors from penetrating the exterior of the work area. Normally only the operator's hands project into the work area. While such apparatus permits removal of the toxic vapors from the open top of a sump tank, or basin bearing liquid chemicals along with vapors generated or penetrating the areas to the side of such sump tanks or liquid chemical containing basins, such apparatus is complicated and expensive. Representative of such approaches are U.S. Pat. No. 3,728,866 to Howard M. Layton, issued Apr. 24, 1973, and U.S. Pat. No. 4,179,984 to Raymond A. Gorcey, issued Dec. 25, 1979.
It is, therefore, a primary object of the present invention to provide an improved dual lid type coal washability table with built-in air ventilation which operates effectively to remove toxic vapors in the work area above an open top sump tank bearing organic chemical liquids or the like and in the work area to the rear and sides thereof.
It is a further object of the invention to provide such a dual lid type coal washability table which does not interfere with the normal test procedure and which readily permits the sealing off of both the sump tank itself and a recessed sink borne by the testing table and opening at its center to the top of a sump tank which depends therefrom.
It is also an object of the present invention to provide such an improved dual lid type coal washability table with built-in air ventilation in which the air ventilation means for the table may be readily coupled to a main vapor removal duct commonly servicing a plurality of similar testing tables to either end thereof.